Manufacture of insulated conductors



Oct. 10, 1933. c. H. ELLIS MANUFACTURE OF INSULATED CONDUCTORS Filed April 26, 19:50

' INVENTOR .3 .JWW M m a Patented Got. 10, 1933 psi STATES MANUFACTURE OF HNSULATED CONDUOTORS Charles H. Ellis, Kenmore, N. Y., assignor to General Cable Corporation, New York, N. Y., a corporation of New Jersey Application April 26, 1930. Serial No. 4417,755

8 Claims.

The present invention relates to vulcanizing processes and to articles in the manufacture of which such processes are utilized.

It is an object of the present invention to provide an improved process for eifecting vulcanization, as well as improved articles of manufacture.

Other objects of the invention will be apparent from the following specification, wherein a preferred and illustrative application of the invention has been selected for description, it being understood, however, that the invention is adaptable to a variety of other applications which will be apparent to those skilled in the art.

In the accompanying drawing- Fig. 1 is a view of a short section of insulated conductor illustrating one embodiment of the invention at an intermediate stage in the manufac turing process, the sheath of insulating material and coatings of accelerator being partially removed; and

Fig. 2 is a similar view but illustrating another embodiment of the invention.

Referring to the particular embodiment of the invention shown in Fig. 1 of the drawing, the first step in the construction of the insulated conductor conveniently comprises the application of an accelerator to a metallic conductor 1 so as to form thereon a coating 2. The accelerator is preferably of the migratory type, that is, one which is adapted to migrate through rubber and quicken the vulcanizing process. Conveniently, such accelerator may comprise the carbon bisulphide derivative of the reaction product of a secondary amine and an aldehyde. Under some conditions, it may be desirable to heat the conductor 1 prior to the application of the accelerator so as to expedite the process of vulcanization. I

The next step in the production of the insulated conductor comprises the positioning of an insulating covering 3 around the metallic conductor l and over the accelerator coating 2. The covering 3 is conveniently formed wholly or in large part of vulcanizable material which includes rubber and a vulcanizing agent, such, for example, as sulphur. The covering 3 may be applied in any suitable manner, as by so-called strip application or by passing the coated metallic conductor 1 through a tubing machine,

wherein the covering 3 is extruded on the metallic conductor 1.

Under certain conditions it may be desirable to apply a coating 4 of the accelerator to the outer surface of the rubber covering 3, but, generally,

'1 this step may be omitted and the covered wire passed directly into a heated vulcanizing apparatus of suitable design, wherein the covered conductor is subjected to a predetermined vulcanizing heat. Conveniently, the movement of the covered conductor through the vulcanizing appa ratus is timed so that, as it passes therefrom, vulcanization is completed to the desired extent,-a1l as will presently appear in greater detail. The next step may conveniently consist in the provision of an additional mechanical and electrical protective covering of convenient design, but this has not been shown in order to simplify the description of the invention.

Practical experience has shown that this process is characterized by a number of important results. For example, vulcanization is accomplished at a rate heretofore considered practically impossible. Under most conditions, a saving in time of from to is eifected. Hence, a material reduction in equipment and labor is made possible, with consequent lowering of the manufacturing cost of the finished conductor. However, as a result of the rapid vulcanization, the undesirable sulphide coating generally found on the metallic conductor is entire- 1y absent and the surface of the conductor remains substantially clean throughout the vulcanizing process.

Another advantage of the present process is the accurate control of the vulcanization which may be obtained. This is due to the fact that the migratory accelerator is applied to one portion of the rubber covering 3, while the vulcanizing heat is applied to another portion. As a consequence, the portion of the covering 3 immediately surrounding the metallic conductor 1 is cured first, and as the migratory accelerator works from the center radially outwardly, the extent of the fully cured area gradually increases until it reaches the outer surface, at which time, the 1 covering 3 is fully cured throughout. In this Way, uniform vulcanization is possible.

Generally, however, vulcanization is interrupted before the outer surface portion of the sirable for the rubber in this portion to remain in a more or less plastic or inelastic condition. Experience has shown that rubber in such condition is highly resistant to ozone and constitutes early disintegration of the elastic portion positioned within the outer surface portion.

Coming now to the embodiment of the invention shown in Fig. 2, it will be observed that a covering 3 is fully cured, inasmuch as it is dean effective corona shield, tending to prevent the fabric covering 5, which may take the form of a spiral strip or thread, is positioned directly on a metallic conductor 6 and that a rubber covering '7 is positioned on the fabric covering 5. In this embodiment, the accelerator is conveniently carried by the fabric covering 5 and not directly by the metallic conductor, as shown inFig. 1.

One method of thus positioning the migratory accelerator involves, first, the dissolving of the accelerator in a solvent such, for example, as gasolene' or water emulsion; whereupon the fabric, which is to be applied to the conductor 6, is immersed in the accelerator solution for one or two hours and then dried in the open air. Conveniently, the fabric may be treated with the accelerator solution at an early stage in its formation, as, for example, while on a bobbin; or it may be treated after being applied to the metallic conductor 6. In either event, a deposit of the accelerator remains in the interstices and on the surface of the fabric which serves to expedite the vulcanizing operation and permit the accomplishment of the desirable results noted in connection with the description of Fig. 1. If desirable, the conductor may be provided with an additional suitable covering affording further mechanical and electrical protection.

It will be noted that the invention may be variously modified and embodied within the scope of the subjoined claims.

I claim:

1. The method of manufacturing an insulat ing covering for a metallic conductor, which comprises applying a migratory accelerator to one portion of said covering and a vulcanizing heat of said covering and applying a vulcanizing heat to an outer surface of said covering so as to vulcanize from within outwardly.

5. The method which comprises applying an accelerator to a metallic conductor, covering said conductor with a jacket formed of a vulcanizable material, and vulcanizing said material.

6. The method which comprises applying a fabric carrying a migratory accelerator to a conductor, applying a covering of vulcanizablematerial, and subjecting said covering to a vulcanizing heat.

7. The steps in the method of manufacturing a covering for a conductor, which comprises inc heating the conductor, positioning immediately adjacent thereto an accelerator, and covering the whole with a vulcanizable material.

8. The method which comprises applying an accelerator to a metallic conductor, covering said 155 conductor with a jacket formed of a vulcanizable material, subjecting said jacket to a vulcanizing heat and interrupting vulcanization before the outer surface of said material is fully cured.

CHARLES H. ELLIS. 

